Updated <MemberActivityEventParser> to handle email events

refs https://github.com/TryGhost/Team/issues/1277

- if email events were passed through the parser they had blank actions and objects
- added `opened`, `received`, and `failed to receive` actions for email events
- changed object to equal `an email` for any email events

ghost/admin/app/components/gh-member-activity-event-parser.js

@@ -15,6 +15,7 @@ export default class EventTimeline extends Component {
             let object = this.getObject(event);
             let info = this.getInfo(event);
             let timestamp = moment(event.data.created_at).fromNow();
+
             return {
                 member_id: event.data.member_id,
                 icon,
@@ -63,6 +64,18 @@ export default class EventTimeline extends Component {
 
             return 'changed';
         }
+
+        if (event.type === 'email_opened_event') {
+            return 'opened';
+        }
+
+        if (event.type === 'email_delivered_event') {
+            return 'received';
+        }
+
+        if (event.type === 'email_failed_event') {
+            return 'failed to receive';
+        }
     }
 
     getObject(event) {
@@ -74,6 +87,10 @@ export default class EventTimeline extends Component {
             return 'their subscription';
         }
 
+        if (event.type.match?.(/^email_/)) {
+            return 'an email';
+        }
+
         return '';
     }